Process of recovering lactose or milk sugar from milk or whey



Patented July 8,1924.

. UNITED STATES I 1,500,770 PATENT OFFICE.

ROGER WM. RYAN, OF OCONOMOWOC, WISCONSIN, ASSIGNOR 'IO CABNATION'- MILK PRODUCTS COMPANY, OF. SEATTLE, WASHINGTON, A CORPORATION OF DELA- WARE.

PROCESS or ancovnamemcrosnoa mm: siren mm MILK on WHEY.-

No Drawing.

To all whom it may concern:

Be it known that I, Room: W. RYAN, a citizen of the United States, and a resident of the city of Oconomowoc, in the county of Waukesha and State of Wisconsin, have invented a new and useful Process of Recovering Lactose or Milk Sugar from Milk or Whey, of which the following is a full, complete, and exact description. 1

This invention relates to an improved process of recovering lactose or milk sugar from milk or whey. Whey is a by-product of cheese factories, and it contains, when fresh, practically all of the lactose originally present in the milk. In the process of cheese making thegreater part of the casein and fat is removed from whole milk. Therefore the residue is a much more con venient source of lactose than the original milk. It contains from 4.5% to 6% lactose, .8% protein, (chiefly albumen), 1% to 2% of mineral elements, (chiefly calcium and magnesium salts), and a variable amount of lactic acid depending on the age of the whey and other conditions, and usually varying from about 2% to .8%.

In certain processes for recovering lactose, as now known in the art, whey is concentrated in vacuum pans at about 140 to 150 F., andis admitted to the pans as fast as evaporation takes place, so that the level of the Whey in the pans is always practically constant. e r

When the whey is concentrated to about Baum it will have about to.60% solids consisting of lactose or milk sugar 46 to 50%, 2 to 3% butter fat, and varying amounts of protein and salts, part of which are suspended in the syrup rather than in solution. It is then removed from the vacuum pans and conducted to crystallizing tanks, where it is cooled by means of coils placed within the tanks. When the temperature reaches about 68 F., the lactose begins to crystallize. The resulting mass is a yellowish moist substance quite similar in its appearance and texture to an ordinary crude cane or beet sugar. product is then centrifuged, and as it third is in the form of a heavy syrup. This syrup still contains much lactose, and therefore live steam is passed throughthe syrup to coagulate the albumen which forms a emerges from the centrifugals about one Application filed February 28, 1920. Serial No. 361,957.-

crust after the syrup has been drawn off.

The syrup is now free of protein, and is again conducted to vacuum pans and crystallized, centrifuged, etc. The resulting second crop of lactose recovered yields from .3% to .6%, and as the first crop would yield about 3.8% lactose the maximum yield acid is precipitated by adding magnesium sulphate. It is then raised to a temperature above boiling point, which results in the precipitation of mineral salts and their collection in the bottom of the vessel. The liquid is then run through filter presses and thence to vacuum pans, where it is concentrated to about 32 or 33 Baum, and consists of about sugar. This product is crystallized, as above described, centrifuged, dried by hot air and then cooled and ground-to a fine powder. This final product is clean and perfectly white.

-Some manufacturers in the preparation of lactose have added to of alum,

(aluminum sulphate),- and after careful coagulation of the protein and filtering of the Whey, have endeavored to neutralize the acid calcium phosphate and the lactic acidsubseity, and to decompose the alum by the addition of lime or milk of lime.

The inter-action between the lime or milk of lime, (calcium hydroxide) and alum, (aluminum sulphate) produces slightly soluble calcium sulphate, together with a gelatinous aluminum hydroxide. This aids mechanically in the removal of protein, but

in-the heating of whey after the addition of lime to coagulate protein there is great danger of decomposing the lactose. It has been found that lactose decomposes to a considerable extent in alkaline solutions: Some manufacturers have sought to avoid the danger of this decomposition of lactose in alkaline solutions by adding sufficient acid to neutralize the solution or render it slightly acid in addition to precipitating calcium sists salts as' the slightly soluble sulphate. Great difiiculty has been found in successfully accom lishing this result. A slight excess of sulpliuric acid which is commonly used, will again cause the decomposition of lactose. Thus, when the whey is heated in an alkaline solution or when acidified with mineral acids, such as sulphuric or phosphoric acid, decomposition of lactose takes place, resulting in a decreased yield. In addition the solubility'of the calcium sulphate which is formed causes a loss of lactose.- This is due to the entrainment of the lactose in the molasses from the whey, which has been concentrated to the crystallizing oint, and the lactose removed as complete y as possible. After several crystallizations of lactose have been made the remaining molasses is practically valueless.

In addition it has been found very difiicult to secure a maximum removal of the protein in these prior art processes. Protein can be precipitated at two points. First, that of 2% acid calculated as lactic acid, and second at the point of very slight acidity, viz, from 0.001% to 0.004% normal, using phenolphthalein as an indicator, In practice I have found the second method to be much superior in point of protein .removal, but have experienced great difiiculty in securing acidity within the limits named. In addition the higher acidity increases the solubility of calcium and magnesium salts, and for this reason is to be avoided.

My present improvement therefore conin a simple and effective process for-recovering lactose from milk, or whey, whereby a maximum yield" of lactose, as wellas of the protein constituent may be obtained.

To this end by invention consists in addin to whey which has been partly clarified by the addition of about '11-% alum and then boiled,-filtered and cooled, such amounts of lime or milk of lime as will neutralize the acidity due to lactic acid, acid calcium phos phates and alum, and will decompose the alum and also provide a slight excess of alkalinity to insure the decomposition of the alum and to cause the removal of nitrogenous matter, such as protein by forming insoluble calcium carbonate upon the introduction of carbon dioxide gas into the whey. The carbon dioxideacts to neutralize the excess lime, precipitating it as calcium carbonate, and precipitating the calcium sulphate resulting from the decomposition of alum in the form of calcium carbonate.

The carbon dioxide further efl'ects the precipitation of ur a1 calcium and magnesium salts of the original milk as carbonates. Suficient additlonal carbon dioxide is introduced into .the solution to give it an acidity of about 01% normal. Carbon dioxide when dissolved in water forms carbonic acid H 00 .water and a very ractically all of the nat-.

serving to neutralize-alkaline solutions and to precipitate alkaline earth metals and their salts as their carbonates. The carbon dioxide also acts to cause the phosphorus constitu-' The whey is now heated to 180 or above is due very largely influence.

to coagulate the nitrogenous matter and to decompose acid phosphates and carbonates of calcium and magnesium which are pro-- duced by the execess carbon dioxide. The

heating is'continued until the acidity of the solution has been lowered to from .001 to .004 normal. This decrease in the acidity is due to the decomposition of the excess carbonic acid upon heating into. gaseous carbon dioxide which is liberated. After filtering the clear filtrate is condensed to the crystallizing point and the lactose then recovered in the usual manner.

- Calcium sulphate has a solubility of .178 parts per in hot water and .17 100 in cold water, while calcium carbonate has a solubility of only .088 per 100 in hot low solubility of only .0013 per 100 in cold water. Thus the solubility of the carbonate is less than .01 of that of the sulphate in moderately cold water.

In addition sulphate of magnesium, which is formed when sulphuric acid is used as the neutralizing agent, is very soluble in water. 26.9 parts of magnesium sulphate are soluble in 100 parts of cold water and 73.8 per 100 in hot water. Magnesium carbonate is very slightly soluble in hot water, viz, .0106 parts per 100. Therefore it is seen that in the ordinary method of recovering lactose all of the magnesium salts remain in the clarified whey. Since the magnesium salts make up about 8% of the total mineral constituents of whey, this will cause a considerable loss of lactose in the final molasses. In addition to this the lime used in neutralizing the acidity contains from 5% to 40% This oxide would interact of the whey magnesium oxide. with the sulphuric acid to form soluble magnesium sulphate.

Thus it is apparent that by the useof carbondioxide in the manner above described, it is possible to secure the almost complete removal of calcium and magnesium salts,

both those which are natural to the milk and 9 parts per tein possible. Accordingly there will be a much smaller'loss in t e final stallizable molasses owing to the decrease content of calcium and magnesium salts, as well as the decreased protein content.

' Finally I have found that a slight excess o'ffthe carbonic acid will not, decompose lactose as is the case with mineral acids, such as sulphuric and phosphoric acid. Hence it is possible to obtain, by means of my'improved process, much higher yields of lactose than the processes now in general use will roduce.

It IS to be noted that the carbon dioxide, CO lS introduced into the milk or whey t after it has been neutralized with lime. In

this way I secure a maximum precipitation of protein and at the same time an almost complete removal of calcium and magnesium salts as their neutral'carbonates.

. In actual practice the improved rocess has been found to give excellent res ts, and

while I have herein described, a articular manner in which the process may e carried out, it is, nevertheless, to be understood that the successive steps of the process as described are susceptible to certain modifications, and I accordingly reserve the priv-,

ilege of resorting to such 1e 'timate changes as may be fairly embodied in the spirit and scope of the invention as claimed.

What I claimis:

1. In the process of recovering lactose from milk or whey which has been first partially clarified by the addition of alum and by then boiling, filtering' aiidlcooling the m1lk or whey adding lime to the par- I 'tially clarified m1lk or'whey in 'sufiiclent quantity to neutralize acidity, and produce an excess of alkalinity, and then introducing carbon dioxide into the solution in sufficient quantity to neutralize the excesslime and precipitate the same together with the naturally occurring calcium and magnesium as.

carbonates.

2. In the process of recovering lactose from milk or whey which has been first partially clarified by the addition of alum and by then boiling, filtering and cooling the milk or whe adding lime to the partially clarified mi or whey in suflicient quantity to neutralize acidity, and produce an excess of alkalinity, introducing carbon dioxide into the solution while in substantially itsori inalvolume in suflicient quantity to neu-' presence of two subscribing witnesses.

ROGER WM. RYAN.

Witnesses: t

Geo. Gunmen,

Cms. H. SGHUELE. 

